PIC16F87XA
6.0
TIMER1 MODULE
The Timer1 module is a 16-bit timer/counter consisting
of two 8-bit registers (TMR1H and TMR1L), which are
readable and writable. The TMR1 Register pair
(TMR1H:TMR1L) increments from 0000h to FFFFh
and rolls over to 0000h. The TMR1 Interrupt, if enabled,
is generated on overflow, which is latched in interrupt
flag bit, TMR1IF (PIR1<0>). This interrupt can be
enabled/disabled by setting/clearing TMR1 interrupt
enable bit, TMR1IE (PIE1<0>).
Timer1 can operate in one of two modes:
• As a Timer
• As a Counter
The operating mode is determined by the clock select
bit, TMR1CS (T1CON<1>).
In Timer mode, Timer1 increments every instruction
cycle. In Counter mode, it increments on every rising
edge of the external clock input.
Timer1 can be enabled/disabled by setting/clearing
control bit, TMR1ON (T1CON<0>).
Timer1 also has an internal “RESET input”. This
RESET can be generated by either of the two CCP
modules (Section 8.0). Register 6-1 shows the Timer1
control register.
When the Timer1 oscillator is enabled (T1OSCEN is
set), the RC1/T1OSI/CCP2 and RC0/T1OSO/T1CKI
pins become inputs. That is, the TRISC<1:0> value is
ignored, and these pins read as ‘0’.
Additional information on timer modules is available in
the PICmicro™ Mid-Range MCU Family Reference
Manual (DS33023).
REGISTER 6-1:
T1CON: TIMER1 CONTROL REGISTER (ADDRESS 10h)
U-0
—
bit 7
U-0
—
R/W-0
R/W-0
R/W-0
T1OSCEN
R/W-0
R/W-0
R/W-0
bit 0
T1CKPS1 T1CKPS0
T1SYNC TMR1CS TMR1ON
bit 7-6
bit 5-4
Unimplemented:
Read as '0'
T1CKPS1:T1CKPS0:
Timer1 Input Clock Prescale Select bits
11
= 1:8 Prescale value
10
= 1:4 Prescale value
01
= 1:2 Prescale value
00
= 1:1 Prescale value
T1OSCEN:
Timer1 Oscillator Enable Control bit
1
= Oscillator is enabled
0
= Oscillator is shut-off (the oscillator inverter is turned off to eliminate power drain)
T1SYNC:
Timer1 External Clock Input Synchronization Control bit
When TMR1CS = 1:
1
= Do not synchronize external clock input
0
= Synchronize external clock input
When TMR1CS = 0:
This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.
TMR1CS:
Timer1 Clock Source Select bit
1
= External clock from pin RC0/T1OSO/T1CKI (on the rising edge)
0
= Internal clock (F
OSC
/4)
TMR1ON:
Timer1 On bit
1
= Enables Timer1
0
= Stops Timer1
Legend:
R = Readable bit
- n = Value at POR
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared
x = Bit is unknown
bit 3
bit 2
bit 1
bit 0
2001 Microchip Technology Inc.
Advance Information
DS39582A-page 55
MICROCHIP [ MICROCHIP TECHNOLOGY ]
